The most common embodiment of passenger car automatic transmissions is the so-called torque converter transmission that differs from conventional and automated shifting transmissions primarily by a non-tractive-force-interrupting shifting process. Such passenger car automatic transmissions usually have a hydraulic torque converter startup clutch and are assembled essentially from several plate clutches and a combination of several free-running gears and planetary gearsets. All shifting and coupling processes are here performed via the plate clutches that produce the non-positive-fit connection of the planetary gearsets connected one after the other to the input and output shaft of the automatic transmission. The individual planetary gearsets are assembled in a known way from the coaxial components, sun gear, planet carrier, and ring gear, as well as the planet gears that can rotate in the planet carrier at a constant axle distance. The drive takes place by means of the sun gear while the rotational movement is transmitted via the planet gears to the planet carrier (driven shaft) and the rolling of the planet gears in the ring gear produces a corresponding transmission ratio.
The support of the planet gears in such planetary gearsets is known, for example, from DE 44 18 693 C1, DE 198 04 734 A1, or DE 103 34 880 A1 and is formed essentially from two side walls that form the planet gear carrier and are arranged parallel to each other and hold a plurality of planet gear pins in multiple coaxial opposing axial holes. The planet gears are supported on these planet gear pins so that they can rotate by means of radial rolling bearings that are inserted into central planet gear holes and are usually formed as needle rings or as solid roll needle sets and are permanently lubricated by means of axial and radial lubricant feed lines within the planet gear pins. In addition, between the side walls of the planet gear carrier and the axial sides of each planet gear there are two circular ring-shaped contact discs that are formed as wear protection of the usually unhardened planet gear carrier and the planet gears, as well as the axial contact for the radial rolling bearings of the planet gears. So that these contact discs cause no lubricant blockage in the radial rolling bearings of the planet gears, which could lead to an undesired temperature increase of the lubricant and the radial rolling bearing due to the through-tumbling of the blocked lubricant quantity, it is known through the specified publications to discharge the lubricant either via recesses formed at the inner diameter of the contact discs or through chord-like grooves in the plant gear pins through the contact discs.
A disadvantage in such a plant gear bearing, however, is that contact discs between the planet gears and the planet carrier produce high power losses due to the sliding friction occurring between the carrier and the planet gears, so that such planetary gearsets cannot satisfy the high energy efficiency required in modern passenger car automatic transmissions. Likewise, the known measures for contact discs for improving the lubricant flow through the radial rolling bearings have proven inadequate, because the lubricant flow guided through the recesses in the contact discs is stopped by the side walls of the planet carrier on the back side of the contact discs and thus results as before in the undesired lubricant blockage in the radial rolling bearings of the planet gears. In addition, the known planet gear bearing has also proven disadvantageous in terms of complicated production and installation of the planet gears, because special surface treatment through grinding and honing is required for the axial sides of the planet gears for reducing the sliding friction with the contact discs. The installation of the planet gears in the planet carrier is then realized in a cumbersome way such that first the planet gear pin must be pushed through the axial hole of one side wall of the planet carrier and then the first contact disc is pushed onto the planet gear pin, then the planet gear is inserted with the preassembled radial rolling bearing between the side walls of the planet gear carrier and the planet gear pin must be pushed through the planet gear, in order to finally insert the second contact disc between the planet gear and the other side wall of the planet gear carrier and to push the planet gear pin into the axial hole of the other side wall.